From ancient Greek νηκτός, "floating", "floating".

Nekton is a set of free-swimming animals with well-developed organs of movement that are able to overcome the force of currents. Nekton organisms make vertical and horizontal movements, which sometimes reach long distances. The nekton include fish, squid, whales, aquatic turtles, sea snakes, amphibians and other animals.

The term "nekton" was first coined by the eminent German biologist Ernst Haeckel in 1891 in his article. Nekton is contrasted with plankton. The intermediate position between them is occupied by micronekton, represented by animals that are capable of limited active movements: juveniles and small species of fish and squid, large shrimps, euphausiid crustaceans.